Microwave polarization rotating device and coupling network



Patented July 7, 1953 MICROWVE POLARIZATION ROTATINGr l DEVICE AND COUPLING NETWORK Charles HrLuhrs, Teaneck, N. Ji, and William J. Tull, Pleasantville, N. `Y., assignors to General Precision Laboratory Incorporated, a'y corporation of New York Application March24, 1949, Serial No. 83,2725

This invention relates to a microwave coupling device and has for'its particular purpose the provision of a device such that microwave energy is freely transmitted in oneidirection but energy transmitted in the opposite direction is either dissipated and prohibited from reaching a terminal point or in the alternative transmitted to and through a branching` network while at the same time being prohibited from transmission to the terminal or origin for energy transmitted in the first mentioned direction. Thus one of the purposes of the invention is to provide a coupling device which is unilateral in its direction of transmission or which may act as a duplexer. That is, energy may be transmitted froma generating source directly to an antenna for radia tion thereby but energy received by the same anftenna is prohibited from being transmitted to the generating source and instead is transmitted through a branching circuit to a suitable receiver. f In accomplishing the purpose of this invention use is made of a phenomenon discovered to obtain in the case of microwaves which if not identical to the Faraday effect as it relates-to polarized light waves is at least akin thereto.

In 1845 Michael Faraday discovered that when plane polarized light was transmitted through a block of `glass subjected to a strong magnetic field in the direction of propagation the plane of vibration of the light was rotated. Subsequent to Faradays early discovery vthe same phenomenon was observed in ymany solids, liquids and gases, the direction or rotation always being in the saine direction regardless of the direction 12 Claims. (Cl. S33-98) and ferrites the latter having the general for greater or' less degree insofar as' microwave energy is concernedwhile other substancespar.-

ticularly applicable as regards the rotationof` light waves'v yield nomeasurable amount of rotation of microwave energy. kFor example, nitrobenzene which exhibits considerable effect on polarized light waves produces no measurablero-jy tation in the microwave region.

Those substances which do affect `microwave energy to a considerable extent include polyironsV mula ROjFezOi in which R 'stands for a bivalent metal ion.

special interest bei-ng the ferrites having a cubic; crystalstructure, namely those containing the bi--'j valent vions of magnesium,zinc,A copper, nickel,

iron, cobalt, `manganese' and mixtures thereof.

The'phenomenon of the Faraday eiiectA or one akin thereto, as'referred to above, is'utlized in the present invention by rproviding a wave' guide structure 'of' s uchjform that' microwave energy introduced at jone'end and rotatedby the application of a magnetic eld isinthe properv plane to be frech7 transmitted through the op-Y be incapable of transmission kthrough the rst mentioned end of the structure.V The energy of propagation of the energy. The amount of rotation is usually given by the formula 0=VHL where 0 is the angle of rotation, H the magnetic field strength, L the length of the path ythrough the affecting substance and V a constant for any particular substance known as the Verdet constant. n

This phenomenon, heretofore, considered to exist only as respects polarizedlight waves 'has' been discovered to likewise exist in the case of microwave energy. at least if the effect is not identical with what is known as'the Faraday effect, it has been discovered that various sub? stances when inuenced by a magnetic fleldhave the power to cause a circumferential rotation oi the microwave energy which rotation is the same regardless of the direction of propagation of en:` ergy depending only on the direction'of the magnetic iield.

Various substances exhibit thisy effect to a y clearly understood from 4the following detailed description when taken in connection with the* 4c 1 transmitted tin 'the last stated ldirection isjre-T iiected before reaching the end of the structure and transmittedto a branch where it is either dis:

sipated or used in other apparatus thus causing the device to act as akduplexer.

The exact nature ofthe invention will be more attached drawings in which: Figure 1 ris a view in elevation of a structure incorporating the principles of the invention.

Figure 2 is ja sectional View taken on the line 2f2-of Figure 1.`

Figure 3 is a sectional viewta'ken on the line 3 3 of Figure l lockingin the direction of thel arrows. J i Figure 4 is a sectional view taken on the line 4-4 of `Figure 1 looking in the direction of the arrows. Figure 5 is a sectional View similar to that of: Fig. 2"but illustrating a'modiiied arrangementv for producing the requisite magnetic held.

vFigure 6y isy an illustration of a field pattern ofA microwaveenergy in one portion of the device.

These substances are particularly adapted for use inthe present invention, those of For the purposes of the following description it will be assumed that it is desired to transmit microwave energy from left to right in the structure of Fig. 1 but to suppress transmission from right to left or to cause energy traveling in this direction to be transmitted to a branch circuit.

Microwave energy is impressed on a Section of rectangular wave guide from any desired source such as a generator (not shown) which may be coupled to the wave guide fitting I2 in a manner as is well known in the art.

The rectangular wave guide II is joined to a circular wave guide section I3 and this junction may comprise a quarter wave transformer I4 as illustrated or may comprise a tapered junction or any of the other well recognized means for providing transition from rectangular to circular wave guide.

The opposite end of the circular wave guide I3 is connected to another section of rectangular wave guide I6, a suitable coupling device II being used to permit transition from circular to rectangular wave guide. A fitting |8 affixed to the end of the section I6 permits any desired apparatus to be connected thereto.

As indicated in the cross-sectional view of Figure 3 the rectangular wave guide section II is connected to the circular wave guide section I3 in such fashion that the longer faces of the rectangular guide are in a horizontal plane. On the other hand as indicated in the cross-sectional view of Fig. 4 the rectangular guide I6 is connected to the circular guide section I3 in such fashion that the longer faces are at an angle to the horizontal. Thus the plane of the rectangular wave guide IB is rotated with respect to the plane of the rectangular wave guide I I and in the example here illustrated the wave guide section I6 is rotated as respects the wave guide II in a counterclockwise direction by approximately 45 degrees.

Other amounts of rotation may be used, however, depending on the rotation given the polarization of the microwave energy which depends on a number of factors as will appear more fully hereafter.

For the present it is sufficient to note that in the structure as illustrated, if microwave energy is introduced in the rectangular section in the TE1,o mode and transmitted to the circular section I3 where it takes the TE1,1 mode it must be rotated in this section by an angle of approximately 45 degrees in a counterclockwise direction in order to be transmitted through the rectangular wave guide section I6, again in the TELO mode.

This rotation of the microwave energy is accomplished by the apparatus most clearly disclosed in Fig. 2. A disk of material 2|, which when a magnetic field is impressed thereon exhibits the property of rotating the plane of polarization of the microwave energy transmitted thereto, is inserted in the circular Wave guide section I3 filling the bore thereof. The rotation of the plane of polarization of the microwave energy depending on the nature of the material of the disk 2 I, its thickness and the magnetic field impressed thereon constitutes the Faraday effect discussed above and if not identical thereto is at least so similar in it results as observable by tests as to be considered the equivalent thereof for the present purpose. Therefore, for the sake of brevity this phenomenon will hereinafter be referred to as the Faraday effect without qualification.

As heretofore stated various materials may be used to produce this effect, polyirons and ferrites and particularly ferrites having a cubic structure being especially useful. For example, a ferrite consisting of manganese oxide, zinc oxide and ferric oxide in the proportions of 25 mols of manganese oxide, 25 mols of zinc oxide and 50 mols of ferric oxide sintered at 1300 C., ground and the resultant mixture pressed in the form of a disk has been found to give excellent results. Such a material having a thickness of .051 inch when subjected to a magnetic field of 2000 gauss has the ability of rotating the plane of polarization of microwave energy having a frequency of 9500 megacycles by an angle of 45 degrees and hence for the purposes of explanation of the instant invention the disk 2| will be considered to be composed of such material having this thickness.

In order that multiple refiections of the microwave energy will not be produced by mismatch between the disk 2| and the circular wave guide I3 which would lead to a distribution of polarization of the microwave energy in the wave guide at the left of the disk 2|, matching pieces 22 and 23 are positioned on either side of the disk 2|. These pieces have a dielectric constant of the order of in the case of the material used as an example herein, and the surfaces thereof which are directed away from the disk 2| are tapered to reduce reflections because of differences in impedance between the hollow wave guide and the material of the matching impedance in a manner as is well understood in the art.

The requisite magnetic field is provided in the form illustrated in Figs. l and 2 by encircling the wave guide I3 with a pair of pole pieces 24 and 26 positioned at each side of the disk 2|. rIhese pole pieces composed of steel or the like are provided with flattened faces against which the faces of a pair of U-shaped permanent magnets 2l and 28 abut. The magnets 21 and 28 are so located with respect to the pole pieces and each other that like poles engage the same pole piece and husy a magnetic field is created which extends through the disk 2| longitudinally of the axis oi the wave guide I3.

The same effect may alternatively be produced by an electromagnetic structure as illustrated in Fig. 5 wherein a coil 3| energized from a source indicated by the conductors 32, 33 supplies the longitudinal magnetic field for the disk 2|.

In either case a longitudinal magnetic field is impressed on the disk 2| which, if the disk is Vcomposed of the material and is of the thickness given in the above example, should be of the order of 2000 gauss.

Thus microwave energy which is introduced in the wave guide section I I and which has a plane of polarization as indicated by the vectors in the cross sectional view of Fig. 3 has its plane of polarization rotated by an angle of 45 degrees in a counterclockwise direction as a result of the Faraday effect produced by the disk 2| having the magnetic field impressed thereon. Inasmuch as the wave guide I6 has its transverse axis rotated by the same amount in the same direction, the plane of polarization of the microwave venergy impressed on this section as illustrated by the voltage vectors of Fig. 4 is such as to permit free transmission thereby and energy impressed at the end of the structure carrying the fitting I2 is freely transmitted therethrough, the

has a plane of polarization as indicated by the voltage vectors of Fig. 4 and this plane of polar-A ization is rotated in ra counterclockwise direction by an angle of substantially 45 degrees as a result of the Faraday effect produced by the disk 2l and its Aassociated magnetic eld. Thus the energy existing in the left hand end of the circular wave guide I3 has a plane of polarization as indicated by the voltage vectors of Fig. 6 and this plane of kpolarization is such as to preclude transmission of such energy through the rectangular wave guide section II. This energy is, therefore, reflected from the junction of the rectangular wave guide section II with the circular wave guide section i3 and in order that the reflected energy be abstracted from the structure thus far described the side arm or branch circuit 3d is provided. v b

This side arm is connected to the circular wave guide i3 with its long dimension extending longitudinally of the axis of the section I3 and extends in a direction at right angles to the wide face of the rectangular wave guide II. The side arm 34 may also be provided with appropriate matching devices as is well understood in the art. Additionally the side arm is vconnected to the circular wave guide I3 at a point whose distance and the circular section I3 is substantially Nkg 4 cerned and no TR and ATR switches or otherl What is claimed is:

l1. A microwave coupling device comprising, a round wave guide section khaving a lfirst rectangular wave guide section coupled to one end rthereof and a second rectangular wave guide section coupled to the opposite end,l the transverse axis of said second rectangular wave guide section being disposed at an angle to the transverse axis yof said first rectangular wave guide section', a member disposed in said round wave guide section transversely tothe axis thereof composed of finely divided material of the group'comprising polyirons and ferrites pressed in the form of a disk and means for impressing a magnetic field on said disk member. 1 f

2. A' microwave coupling device comprising, a

such devices need be employed.

roundA Wave guide section having a first rectangular wave guide section' coupled to one end thereof and a second rectangular wave guide section coupled to the opposite end, the transverse n tion transversely to the axis thereof composed where N is any odd integer-including I and Xg is n the wave length of the microwave energy in the wave guide.

Thus the reflected energy is in the proper phase and Diane of polarization to be transmitted into and through the side arm 34. The energy so transmitted may be dissipated in a dissipative load connected to the fitting 36 or a utilization circuit may be connected thereto.

For example, where it is desired to use'the inu stant invention as a duplexer, a microwave generator may be connected to the fitting I2, an antenna to the fitting `I8 and a receiver to the tting 35. Under such circumstances energy produced by the generator will be transmitted directly to the antenna for radiation thereby, none being introduced into the side arm 34 because the plane of polarization is such as to bypass this connection. On the other hand energy received by the antenna cannot be impressed on the microwave generator because its plane of polarization is such as to vbe improper for transmission in Ythe rectangular wave guide section kI I.. Instead this energy is reiiected and since its vplane of polarization is at an angle of 90 degrees as respects 'the generated energy it is in such a plane as to be freely transmitted through the side arm 34 and hence to the receiver.

Therefore, by use -of Lsuch an arrangement energy may be transmitted and received by a single antenna while at the same time the generator and receiver are isolated from each other as far as the direct interchange of energy is contion coupled to the opposite end, the transverse axis of said second rectangular wave guide section being disposed at an angle to the transverse axis of said first rectangular Wave guide section, a member disposed in said round wave guide section transversely to the axis thereof composed of a nely divided material of the'class of ferrites having a cubic crystal structure pressed in the form of a disk and means for impressing a mag netic field on said disk member.

4.AA microwave coupling device comprising a round wave guide section having a rst rectangular wave guide sectionk coupled to one end thereof and a second rectangular wave guide section coupled to the opposite end, the transverse axis of said second rectangular wave guide section being disposed at an angle to the transverse axis of said irst rectangular wave guide section, a member disposed in said round wave guide section transversely to theaxis thereof composed of Vfinely divided rmanganese oxide, zinc oxide and ferrie oxide intimatelymix'ed in substantially the proportions of 25 mols of manganese oxide, 25 mois of zinc oxide and 50 mols of ferrie oxide and pressed in the form of a disk land means for impressing a magnetic eld on said disk member.

portions of 25 mols of manganese oxide, 25 mols of zinc oxide and 50 mols of ferric oxide and pressed in the form of a disk, impedance matching members having high dielectric constants disposed adjacent the opposite surfaces of said disk member and means for impressing a magnetic field on said disk member.

6. A microwave coupling device comprising, a round wave guide section having a rst rectangular wave guide section coupled to one end thereof and a second rectangular wave guide section coupled to the opposite end, the transverse axis of said second rectangular wave guide section being disposed at an angle to the transverse axis of said first rectangular wave guide section, a member disposed in said round wave guide section transversely to the axis thereof composed of finely divided material of the group comprising polyirons and ferrites pressed in the form of a disk, means for impressing a magnetic field on said disk member and a side arm wave guide section connected to said coupling device intermediate said first rectangular wave guide section and said disk member.

7. A microwave coupling device comprising a round wave guide section having a first rectangular wave guide section coupled to one end thereof and a second rectangular wave guide section coupled to the opposite end, the transverse axis of said second rectangular wave guide section being disposed at an angle to the transverse axis of said first rectangular wave guide section, a member disposed in said round wave guide section transversely to the axis thereof composed of a nely divided material of the class of ferrities having a cubic crystal structure pressed in the form of a disk, means for impressing a magnetic field cn said disk member and a side arm wave guide section connected to said coupling device intermediate said rst rectangular wave guide section and said disk member.

8. A microwave coupling device comprising a round wave guide section having a first rectangular wave guideV section coupled to one end thereof and a second rectangular wave guide section coupled to the opposite end, the transverse axis of said second rectangular wave guide section being disposed at an angle to the transverse axis of said first rectangular wave guide section, a member disposed in said round wave guide section transversely to the axis thereof composed of iinely divided manganese oxide, zinc oxide and ferrie oxide intimately mixed in substantially the proportions of 25 mols of manganese oxide, 25 mols of zinc oxide and 50 mols of ferrie oxide and pressed in the form of a disk, means for impressing a magnetic field on said disk member and a side arm wave guide section connected to said coupling device intermediate said first rectangular wave guide section and said disk member.

9, A microwave coupling device comprising, a round hollow open ended pipe wave guide transmission section adapted to be excited by microwave energy in a noncircular mode, a solid cylindrical member positioned therein and comprehending the axis of said wave guide section, said solid member being composed of finely divided material of the group comprising polyirons and ferrites pressed in intimate contact, and means for impressing a magnetic field on said solid member, said magnetic field extending through said solid member in a direction parallel to the axis thereof, whereby when said transmission section is excited in said noncircular mode, the plane of polarization of said energy is rotated.

10; A microwave coupling device comprising, a round hollow open ended pipe wave guide transmission section adapted to be excited by microwave energy in a noncircular mode, a solid cylindrical member positioned therein and comprehending the axis of said wave guide section, said solid member being composed of finely divided material of the class of ferrites having a cubic crystal structure pressed in intimate contact, and means for impressing a magnetic field on said solid member, said magnetic ileld extending through said solid member in a direction parallel to the axis thereof, whereby when said transmission section is excited in said noncircular mode, the plane of polarization of said energy is rotated.

11. A microwave coupling device comprising, a round hollow open ended pipe wave guide transmission section adapted to be excited by microwave energy in a noncircular mode, a solid cylindrical member positioned therein and comprehending the axis of said wave guide section, said solid member being composed of nely divided material having the formula ROFezOa where R is a bivalent metal ion pressed in intimate contact, and means for impressing a magnetic field on said solid member, said magnetic field extending through said solid member, in a. direction parallel to the axis thereof, whereby when said transmission section is excited in said noncircular mode, the plane of polarization of said energy is rotated.

l2. A microwave coupling device comprising, a round hollow open ended pipe wave guide transmission section adapted to be excited by microwave energy in a noncircular mode, a solid cylindrical member positioned therein and comprehending the axis of said wave guide section, said solid member being composed of a mixture of Iinely divided manganese oxide, zinc oxide and ferrie oxide in substantially the proportions of 25 mols of manganese oxide, 25 mols of zinc oxide and 50 mols of ferric oxide, the particles of the mixture being pressed into intimate contact, and means for impressing a magnetic iield on said solid member, said magnetic field extending through said solid member in a direction parallel to the axis thereof, whereby when said transmission section is excited in said noncircular mode, the plane of polarization of said energy is rotated.

CHARLES H. LUHRS. WILLIAM J. TULL.

References Cited in the Iile of this patent UNTTED STATES PATENTS Number Name Date 2,197,123 King Apr. 16, 1940 2,402,948 Carlson July 2, 1946 2,425,345 Ring Aug, 12, 1947 2,438,119 Fox Mar. 23, 1948 2,442,396 Bubb June 1, 1948 2,508,479 Wheeler May 23, 1950 2,532,157 Evans Nov. 28, 1950 OTHER REFERENCES Ragan, Microwave Transmission Circuits, vol. 9, Radiation Laboratory Series, pp. 645-46 and 660. 

